Geometrical instruments – Gauge – With calibration device or gauge for nuclear reactor element
Reexamination Certificate
2000-09-15
2002-10-15
Fulton, Christopher W. (Department: 2859)
Geometrical instruments
Gauge
With calibration device or gauge for nuclear reactor element
C073S001790, C033S0010MP
Reexamination Certificate
active
06463667
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an improved machine tool precision-measuring apparatus for measuring and rating the machining accuracy of a machine tool.
In a recent field of precision machining technology, a numerically controlled (NC) machine tool is required to provide high-precision machining. The NC machine tool is provided with an actuation-interpolating function for interpolating errors. There are methods for evaluating the function, such as e.g., an actual cutting process and a circular trajectory measuring method.
The actual cutting process includes the steps of: initially cutting a workpiece in practice using an end mill (cutting tool), which is mounted on a spindle of the NC machine tool through a tool holder etc.; then removing the workpiece from the NC machine tool in order to measure using precision measuring equipment how the processed workpiece is shaped; and, assessing errors in such measurements.
The circular trajectory measuring method includes the steps of: mounting a spherical surface receiver on a table of the NC machine tool, which spherical surface receiver has a receiving surface coincident with a sphere, and which receiving surface is made of a magnetically attracting material; positioning the sphere on the spherical surface receiver; mounting a spherical surface seat on the spindle of the NC machine tool, which spherical surface seat is provided with spherical projections, and further which spherical surface seat is made of a magnetically attracting material; placing a length-measuring machine therein, which measures a length using a differential transformer, and then permitting both ends of a radially extending length-measuring bar to be rotatably supported on the sphere and the spherical surface seat with the aid of magnets; then driving the spindle into circular movement about the center of the spherical surface receiver on the table in order to measure variations in length of the length-measuring bar; and, calculating a trajectory of the spindle and then evaluating errors in such a calculation.
However, the actual cutting process is unable to precisely measure a position of the spindle because two different errors commingle in results of the measurement. More specifically, machining errors caused by a cutting tool such as the end mill mingles with errors in trajectories of the NC machine tool.
In addition, the circular trajectory measuring method is unable to accommodate shapes except for an arcuate shape. For example, it is impossible to handle trajectories specified by either linear interpolation or NURBUS interpolation employing a functional equation that expresses a free curve.
In order to overcome the above problems, a measuring apparatus is disclosed in published Japanese Patent Application Laid-Open No. (Hei) 11-58182, as schematically illustrated in FIG.
10
.
Referring to
FIG. 10
, a measuring apparatus
100
is shown having X- and Y-axes directed movable linear guide rails
111
,
112
disposed above a base plate
110
. These two movable linear guide rails
111
,
112
extend in a perpendicular relationship to one another, while being disposed vertically above one another. The X-axis directed movable linear guide rail
111
has both ends positioned on support linear guide blocks
115
,
116
. The support linear guide blocks
115
and
116
are slid on fixed left and right linear guide rails
113
and
114
, respectively. The support linear guide blocks
115
and
116
are movable in the direction of the Y-axis. The fixed left and right linear guide rails
113
,
114
are laid on the base plate
110
along opposite edges of the base plate
110
in leftward and rightward directions thereof, respectively. Meanwhile, the Y-axis directed movable linear guide rail
112
has both ends positioned on support linear guide blocks
119
,
120
. The support linear guide blocks
119
and
120
are slid on fixed front and rear linear guide rails
117
and
118
, respectively. The support linear guide blocks
119
,
120
are movable in the direction of the X-axis. The fixed front and rear linear guide rails
117
,
118
are laid on the base plate
110
along opposite edges of the base plate
110
in forward and rearward directions thereof, respectively. This structure allows the movable linear guide rails
111
,
112
to travel in the directions of the Y and X-axes, respectively.
The measuring apparatus
100
has a main block
121
disposed at a position where the movable linear guide rails
111
,
112
are perpendicular to one another. The main block
121
is formed by a rectangular box. The main block
121
is movable in the directions of the X- and Y-axes. The main block
121
is connected to a machine tool spindle
125
through a connecting shaft
124
. Movement of the spindle
125
causes the main block
121
to be moved in union therewith. In addition, the movable linear guide rails
111
,
112
are moved parallel to the respective directions of the Y and X-axes in association with the movement of the main block
121
.
The movable linear guide rails
111
,
112
have linear scales
126
,
127
mounted thereon, respectively. The linear scale
126
is positioned on the top of the movable linear guide rail
111
along substantially the entire length thereof. The linear scale
127
is disposed on the bottom of the movable linear guide rail
112
along substantially the full length thereof. A position-detecting head (not shown) on the main block
121
reads respective graduations of the linear scales
126
,
127
, thereby allowing positional data on the spindle
125
to be detected. The measuring apparatus
100
having above system is able to measure trajectories of the moving spindle
125
except for circular trajectories of the spindle
125
.
However, the prior art measuring apparatus
100
includes a total of six block portions in the directions of the X- and Y-axes, i.e., three for each direction, which block portions are slid on other members upon movement of the spindle
125
. In addition, six rail members are required in order to support the block portions. The term “block portion” in this text denotes four-support linear guide blocks
115
,
116
,
119
,
120
and two-through holes of the main block
121
. The main block
121
has the through-holes formed therein in the directions of the X- and Y-axes, and further has the linear guide rails
111
,
112
inserted through the through-holes. The term “rail member” used herein refers to the fixed linear guide rails
113
,
114
,
117
,
118
and the movable linear guide rails
111
,
112
.
Consequently, the measuring apparatus
100
is complicated in structure and is made heavier in weight because of such a large number of constitutional members.
Furthermore, when the NC machine tools at different locations are to be measured, then the measuring apparatus
100
is so complicated in structure that it takes time to assemble and disassemble the measuring apparatus
100
. In addition, the measuring apparatus
100
is heavy in weight, and is thus difficult to move. Further, since the measuring apparatus
100
includes a large number of members, it is time-consuming to adjust the measuring apparatus
100
after assembly thereof.
SUMMARY OF THE INVENTION
In view of the above, an object of the present invention is to provide a machine tool precision-measuring apparatus having a simpler structure, lighter weight, and portability.
In the machine tool precision-measuring apparatus fulfilling the above object comprises: a first linear movement distance-measuring means including a first slide shaft, a first slide bush slidably attached to the first slide shaft, and a first distance sensor for measuring a distance that the first slide shaft relatively travels with respect to the first slide bush; and, a second linear movement distance-measuring means including a second slide shaft positioned across the first slide shaft, a second slide bush connected to the first slide bush, the second slide bush being slidably attached to the second slide shaft, and a second distance sensor for measurin
Koya Masahide
Matsuda Hiromichi
Ushio Masaki
Yamaguchi Yoshihiko
Armstrong Westerman & Hattori, LLP
Fulton Christopher W.
Orio Precision Co., LTD
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